Method and means of refrigeration



April 1952 G. c. DEMETRAK METHOD AND MEANS OF REFRIGERATION Filed May 21, 1948 a $2 a w ATTTORNEY.

Patented Apr. 22, 1952 METHOD AND MEANS OF REFRIGERATION George C. Demetrak, San Francisco, Calif., as-

signor to -Perishables Shipping Equipment Company, a corporation of Nevada Application May 21, 1948, Serial No. 28,489

1 Claim.

The present invention relates to a refrigerator mechanism and methods of refrigeration which are self-contained and which find a special usefulness for refrigerated transportation.

It is among the objects of the present invention to provide a self -contained refrigeration unit which is rugged and reliable, minimizing the possible losses of cargo due to failure of refrigeration and providing easy servicing.

It is also an object of the present invention to provide a refrigerating system in which the moving parts are reduced to a minimum.

It is also an object of the present invention to provide a refrigerating mechanism and system which is completely self-contained, carrying its own independent power, which will operate without any outside source of energy.

It is also an object of the present invention to provide a self -contained refrigeration mechanism and system wherein the power used to positively circulate the secondary refrigerant is not in anywise associated with either the primary or secondary refrigerant, but on the other hand is supplied in replaceable units for convenient servicmg.

Further objects are to provide a construction of maximum simplicity, economy, and ease of assembly and disassembly, and such further objects, advantages, and capabilities as will more fully appear and as are inherently possessed by the device and the invention described herein.

The invention further resides in the combination, construction and arrangement of parts illusstrated in the accompanying drawings and while there is shown therein a preferred embodiment it is to be understood that the same is capable of modification and change, and comprehends other details of construction without departing from the spirit or scope of the invention and the. appended claim.

Referring now to the drawings:

Figure l is a diagrammatic arrangement of the complete system of the present invention.

Figure 2 is a vertical section of a gas driven pump used for positive circulation of the secondary refrigerant, taken on the line 2-2 of Figure 1, looking in the direction of the arrows. with a small portion thereof being shown in elevation.

Figure 3 is likewise a view of the gas driven pump shown in Figure 2 in side elevation but turned 90 in a horizontal plane, with a portion being shown in section taken on the line 3-3 of Figure 2, looking in the direction of the arrows.

Figure 4 is a fragmentary section in enlarged scale, taken on the line 4-4 in Figure 3 and looking in the direction of the arrows.

Referring now more particularly to the accompanying drawings in which like numerals are employed to designate like parts throughout the same, and with particular reference to Figure 1, one of the principal elements making up the present system is the closed container Ill. The container I!) may be mounted either in association with the space to be refrigerated or at a remote point. In any event for efficient operation it should be insulated on its exterior against thermal transfer, by insulation H. The container I0 is fabricated of metal preferably and should be built to withstand an internal pressure of the order of 15 p. s. i. The single access to the interior of the container [0 is closed by the cover 12 which normally forms a gas-tight seal. A portion of the interior of the container In is separated by plate M from the main interior chamber I5 to form the chamber [6. Thus there is no contact directly between chamber l5 and chamber I6.

The system employs a heat exchange fluid passing through a closed circuit and for purposes of clarity this fiuid is here termed the secondary refrigerant. Any of the well known substances used in refrigeration such as sulfur dioxide, ethyl chloride, Freon, or the like, may be employed satisfactorily as the secondary refrigerant. By using such a secondary refrigerant instead of one which forms a gas at ordinary operating temperatures, the necessity for gas proof lines and connections, back pressure valves, and other similar fittings, is entirely eliminated.

The secondary refrigerant closed circuit is a continuous confined path. This circuit includes the cooling coils l'l located in the space to be refrigerated 35, and the return line l8 which leads into a surge tank 20, and from thence by line 2| to the gas driven pump 22. The line 2! may be provided with a shut-off valve 23 and a check valve 24 to insure against back flow of the refrigerating liquid. By means of the pump 22 the secondary refrigerant receives the positive moving force required for travel throughout the en tire system. It leaves the pump by line 25 through check valve 26 and goes to the chamber 16 located within the container I0. Inasmuch as the chamber [6 has no contact with any other chamber, it is apparent that the line 25 can empty into this chamber if desired, or the out through the line 21 to the refrigerating coils I! to complete the closed circuit. If desirable the surge tank 28 may be vented to eliminate any possibility of back pressure or the forming of air locks, without departing from the fact that the secondary refrigerant is confined in a closed circuit and Without any contact with the primary refrigerant. The surge tank 20 is not a necessary element of the circuit, although desirable, and may be eliminated, in which event lines l8 and 2| would be joined.

Chamber I5 is the space provided for a primary refrigerant 28. Since sublimating refrigerants such as solid carbon dioxide (Dry Ice) are particularly useful in this type of refrigeration, the invention will be described with Dry Ice as the primary refrigerant. Any primary refrigerant used in the system will contact the wall I4 to cool the chamber I6 and in turn cool the secondary refrigerant, whether released into the chamber IB 'or'confined within the grid 01'' coil 29. If a sublimating refrigerant is used gas pressures within the container It will build 'up very quickly and must be dissipated. Assuming the use of Dry Ice 28 within the container. 10, and sublimated CO2 gas is continuously removed from the chamber I5 by line 30 and maybe dissipated to atmosphere by line 3i. Since CO2 gas is useful as an insulating "medium, a special valve 32 may be installed in the line 30 by "means of which all or a portion of the CO2 gas may be diverted by line 33 and discharged into the insulation 34 surrounding the space to be refrigerated which is designated as 35. All or anyportion of the CO2 gas may be diverted by line 36 to the interior of the refrigerated space 35 since this gas is a definite aid 'to the preservation of some goods. For safety requirementsand better control, valve 31 is interposed in the "exhaust line 3|, valve 38 is interposed in the line 33, andvalve '40 is interposed in the line 36. Asa safety precaution and to prevent any requirements for heavy construction of the container H], a safety valve 41 is provided and set to automatically relieve the pressures produced by the sublimation of the Dry Ice before thetdangerpoint is reached. A setting between "and p. s; i. has been found-to be entirely satisfactory, for the operation of the present system.

The pump 22, which provides the force for moving the liquid in positive circulation through the 'closed system, is here shown as "a 'gas' driven diaphragm pump. While it has been'known to use thesublim'ated COz gas to drive thepump 22, it has been found desirable tousefan independent source of gas power which can be serviced, changed or regulated quite independently of the primary refrigerant and without any reference to it. To accomplish this purpose readily replaceable cylinders 42 of gas 'underpressure are connected "through a two-way valve "'43 to the line 44. For safety and "convenience a shut-off valve 45 may be located injline 44 "adjacent the gas cylinders 42. Any suitableigas may be'used 46 so that the pressure of the 'g'asgoing to the pump can be controlled. Pressures of the order of from 10 to '15 p. s. i. have been found ample for this purpose. Pressure guages 41 may be added to visually indicate the precise pressure in the line "44.

Interposed in the line 44 leading to the pump 4 22, is controlling valve 48 which is directly responsive to and controlled by the pressure responsive means 5B which in turn is controlled by the temperature sensitive member 5! located within the space to be refrigerated 35.

The pump 22 may generally be described as a gas driven diaphragm pump having twin chambers 52 and 53. Each of these two chambers 52 and 53 is divided by diaphragins 54 and 55 respectively. There is no communication between the divided sections of each chamber. The inner division of each chamber is for the liquid secondary refrigerant and the outer division of each chamber is for the gas which furnishes the power actuating the pump. This is so arranged that if there is any liquid leak past the central valve stem 56 the leak will be only into another liquid chamber and no harm will result. The diaphragm's 54 and 55 are reinforced and are secured for positive simultaneous action by means of diaphragm plates 51 secured in spaced relation to the stem 56. The entrance to the liquid side of each chamber is through suction valve 58a for the upper chamber and 5th for the lower chamber. The discharge from each chamber is through discharge valve 6M for the liquid from the upper chamber and 8th for the liquid from the lower chamber. Liquid line 2 attaches to the port GI and the outlet line attaches to the port 52. The valves 58a and are retained within valve cages '63 and are normally held closed by the pressure of springs 64 and 64 suitably restrained within the cages 5 3. Similarly discharge valves a and 58b seat in valve cages 65 and are normally held in closed position by the pressure of springs 66 retained in the cages 65.

Above one of the chambers on the gas side, is a housing 61 which contains a mechanism which causes the pump to operate with an immediate, precision, snap action. It has been found that best results have been obtained by a pump where the diaphragm action is in both directions and the valving of the gas is both positive and fast. The mechanism devised for this purpose, which is only one of numerous ways-of accomplishing the same result, is as follows: -A valve trip lever it loosely engages the button 7! at the upper end of valve stem 56. t its outer and other end, the valve trip lever 10 is pivoted within the housing 61 at 72. Above the pivot point the lever 16 carries a valve actuator spring barrel 13 which contains within it a spring (not shown) which is rigidly restrained at both ends and so capable of compression in both directions. This spring controls the movement of a valve actuator 14 which moves in a lateral directionja-s opposed to the vertical movement of the valve stem '58. The actuator E4 is notched in two places 15 and 19. A valve trip 16 is adapted to engage these notches alternately. The other end-of the valve trip 16 is restrained within the trip lever 79. Due to the length of the valve actuator -74 and to insure proper travel, a valve actuator screw H is provided to pass up through a slot in the actuator 14 and be secured to a boss ingthehousing 61.

The alternate valving of the gas is accomplished by the horizontal movement of the gas valve piston 86 by means of theforked end-of the valve actuator 14.

The gas valve piston Bil moves in response to the actuator "14 in-a multiported valve 8!. The gas from line 44 enters through the port "82 and exhausts through port 83 via line 30a to line 3D.

Operation of the pump-Gas for the operation of the pump 22 is conveyed by line 44 which connects with the gas inlet port 82. The positions of the diaphragms 54 and 55 shown in Figures 2 and 3 indicate that they have almost reached their maximum upward travel and that the valve trip 16 engaging notches is about to disengage permitting the spring (not shown) contained in barrel 13 to move to the left and from the position shown in Figure 3, a suflicient distance to dispose the piston heads to the left of the annular ports 83' and 84' which are shown in the drawings as being disposed to the right thereof.

The flow of the gas in the position shown in Figure 3 is through the inlet port 82 through the annular port 82' into the inner piston chamber 89 thence through passage 88 down through the riser 81 and through the passage 86 to exert pressure on the outer surface of the diaphragm 55. As the central piston stem 56 rises due to this pressure, gas from the upper chamber is exhausted through the passage 96 through annuiar passage 83' to the outlet port 83.

Simultaneously the secondary refrigerant enters through inlet port 6! opening suction valve 58a to permit the flow of the liquid into the liquid side of the upper chamber 52. The pressure in the liquid side of the lower chamber due to exodus of the liquid, plus the force exerted by the spring 64, keeps the valve 582) closed. As the central stem 56 moves upward, the liquid in the lower chamber 53 forces the outletvalve 601) open and discharges through the outlet port 62. The lack of pressure plus the force exerted by spring 66 keeps the outlet valve 601: on the liquid side of the upper chamber 52, closed.

At the moment the central stem 16, and with it the diaphragms 54 and 55, attain their maximum upward movement, the valve trip lever 16 disengages the valve trip 16 which in turn disengages from notches 15 in valve actuator 14. The compression on the spring within the barrel 13 being released causes the valve actuator 14 to move to the left as shown in Figure 3 until the trip lever 16 engages notches 19. In this manner the valve piston 8| is moved to the left of the annular ports 83 and 82 to permit appropriate flow of gas and secondary refrigerant on the down stroke.

The passage of the secondary refrigerant to and through the pump on the downward movement is precisely the opposite of that described for the upward movement. The secondary refrigerant enters the pump through port BI and. into the liquid side of the lower chambers 53 through suction valve 58b. The suction plus the force exerted by the spring 66 keeps the discharge valve 66b in closed position. In the upper liquid chamber the secondary refrigerant is being discharged through the outlet valve 66a to port 62 and from thence into line 25. The pressure of the discharge plus the pressure exerted by spring 64 serves to keep the valve 58a in position so that no liquid enters the upper liquid chamber on the discharge or downward stroke.

The suction of secondary refrigerant into the liquid side of the lower chamber 53 and the discharge of the secondary refrigerant from the liquid side of the upper chamber 52 is again brought about by the pressure exerted by the gas supplied through line 44. The gas enters through port 82 and into the annular passage 82'. The passage of the gas to the left is blocked by the head of valve piston 80, but is free to pass through the passage into the upper portion of chamber 52, thereby supplying pressure on the upper side of diaphragm 54 and causing the two diaphragms 54 and 55 to move downwardly as a unit. As this occurs, gas from the lower chamber is exhausted through passage 56 upwardly through vertical riser 81 through passage 88 to the inner piston chamber 69 which now connects through the annular passage 83' to the outlet port 83.

As the travel of the two diaphragms 54 and 55 and. with them the central stem 56 reach their maximum downward position, instantaneously the trip lever 16 which has been compressing the spring in barrel 73 in the opposite direction causes the valve trip 16 to disengage notches 15 in the valve actuator 14. The compression on the spring being released causes the valve actua-r tor 14 to move to the right (the position shown in Figure 3) whereupon valve trip 16 again enages notches 15.

Operation of the system.-It is apparent that any refrigerant used for the primary refrigeration having extremely low temperatures and atmospheric pressures is far too cold for direct refrigeration, hence the use of a secondary refrigerant which will remain a liquid even at very low temperatures in order to accomplish the varying degrees of refrigeration required, and to establish control at the set temperatures. To place the system in operation the primary refrigerant is placed inside the container It! in chamber l5, and

the cover [2 closed to confine the primary refrigerant therein. The secondary refrigerant, whether confined in the grid or coils 29 or circulating freely within chamber I6, is in heat exchange relation with the primary refrigerant completely separated therefrom by the plate 14.

By adjusting valves 46 and 43 operating gas at the required pressure to operate pump 22 is led via line 44 to the pump which imparts a continuous driving force to the secondary refrigerant as long as the pump is in operation. This pump then, moves the cooled secondary refrigerant from the chamber [6 to the cooling coils H in the space to be refrigerated 35. Here the secondary refrigerant absorbs heat and is returned through the surge tank 20 via line 2| to the pump to complete the cycle. The thermostat 50 is set at the temperature required for refrigeration. If, for example, there is desired refrigerating temperature 15 C., the thermostat 50 is so set and the pump will continue to operate and circulate the secondary refrigerant in the manner described above until this temperature is reached. This information will be conveyed by the thermostatic bulb '5! to the thermostat which will then operate the valve 48 and stop the flow of gas to the pump. This in turn will stop the circulation of the secondary refrigerant in the closed circuit. When the temperature in the space 35 goes above the setting of the thermostat this information will also be conveyed by the thermostatic bulb 5| to the thermostat 56 causing it to open the valve 48 and start the pump and the circulation of the secondary refrigerant. In this manner the temperature of the setting may be maintained at the thermostat setting within a tolerance of i2", for aslong a period as the tank I 0 is supplied or replenished with a primary refrigerant, and there is gas to operate the pump 22.

It will be observed that the gas contained in bottles 42 may be replaced independently, individually, without disturbing the operation of the system. The availability of bottled gas is so universal that the forward progress of this re. frigerated unit need only be delayed long enough to remove the depleted bottle and insert a new one.

- It should be understood that while a particular type of pump has been referred to and disclosed, any type of pump acting on gas pressure may be used in this system. Further, the thermostatic controlled valve 48 may be placed in the secondary refrigerant line 2| instead of the gas line with substantially the same results I claim:

A self contained and readily portable refrigerating system, comprising in combination, an enclosed space to be refrigerated, a separate closed container for an evaporable primary refrigerant, a closed refrigerating circuit for a low temperature liquid refrigerant passing in heat releasing relation with said primary refrigerant without direct contact therewith and passing through said space to be refrigerated in heat absorbing relationship, a separate and readily 8 replaceable source of gas under pressure, means for regulating the pressure of the released gas, means driven by said released gas interposed in said closed circuit for effecting the positive circulation of the secondary refrigerant but without direct contact with said released gas, and thermostatic means for controlling the flow of gas to the said driven means in such a manner as to maintain the temperature of the said enclosed space substantially constant.

GEORGE C. DEMETRAK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 552,481 Kreusler Dec. 31, 1895 2,175,267 Killefie-r Oct. 10, 1939 2,380,537 McMechan July 31, 1945 2,383,486 Isenberget a1. Aug. 28, 1945 2,450,713 Brunsing Oct. 5, 1948 

